1. Technical Field
Photoresist polymers and photoresist compositions containing the same are disclosed that are suitable for a photolighography process using a light source of the far ultraviolet region such as EUV (Extreme Ultraviolet, 13 nm) in production of ultrafine circuits of highly-integrated semiconductor devices.
2. Description of the Related Art
Recently, chemical amplification type deep ultraviolet (DUV) photoresists have been investigated in order to achieve higher sensitivities in ultrafine circuit formation processes. Such photoresists are prepared by blending a photoacid generator and a matrix polymer having an acid labile group.
According to reaction mechanism of such a photoresist, the photoacid generator generates acid when it is irradiated by UV light source, and the main chain or a branched chain of the matrix polymer reacts with the generated acid during a subsequent baking process and is decomposed or crosslinked, so that polarity of the polymer is considerably altered. This alteration in the polarity creates a solubility difference in the developing solution between an exposed area and an unexposed area.
For example, in case of a positive photoresist, acid is generated in the exposed area, and the generated acid reacts with the matrix polymer during the subsequent baking process so that the main chain or branched chain of the polymer is decomposed and dissolved in a subsequent developing process. However, since acid is not generated in the unexposed area, original structure of the polymer is maintained and is not dissolved during the subsequent developing process, thereby forming a positive image of a mask on a substrate.
In any lithography process, resolution is dependent upon the wavelength of the light source. As the wavelength of light source becomes smaller, ultrafine patterns of a greater degree may be formed. As far as exposure equipment required to form patterns of less than 50 nm, EUV equipment is under development, and improved photoresists for patterns of less than 50 nm are also under development. In case of the photoresist, it is expected that significant problems will occur for the successful formation of patterns of less than 50 nm. For example, on one hand, the photoresist will need to be deposited in a very thin film but, on the other hand, thin films cannot ensure sufficient etching resistance. Therefore, there is a need improved photoresists having excellent etching resistance that can be deposited in very thin films for forming patterns of less than 50 nm.